International Journal of Plant & Soil Science

Intercropping—the deliberate co-cultivation of two or more crops in the same space and season—has re-emerged as a cornerstone of climate-smart agriculture because it can raise system resilience while improving soil function. This global review synthesizes evidence on how intercropping, including indigenous and smallholder polycultures, supports climate-smart soil outcomes through (i) biologically mediated nitrogen cycling and (ii) soil organic carbon (SOC) accrual and stabilization. Across regions, intercrops diversify rooting patterns, residue chemistry, and rhizosphere processes, shifting nutrient acquisition from input dependence toward biological regulation. In legume–cereal systems, biological nitrogen fixation, complementary N uptake, and altered microbial enzyme activity can reduce reactive N losses while sustaining yields. In parallel, intercropping can increase SOC by boosting belowground carbon inputs, strengthening aggregation, and promoting microbial processing into persistent forms. Recent studies indicate that intercropping may alter the balance of plant- and microbe-derived carbon contributions and can enhance macroaggregate-associated SOC and microbial necromass—key components linked to SOC persistence. However, intercropping outcomes vary by crop identity, spatial configuration, climate, and management intensity, and benefits can be weakened when high external inputs override facilitative interactions. By integrating indigenous knowledge with contemporary soil biogeochemistry, this review proposes a mechanism-based framework that connects intercrop design choices (species traits, temporal niche separation, and spatial arrangement) to measurable soil functions (N retention, greenhouse-gas outcomes, aggregation, and SOC stabilization). The synthesis highlights priority research needs, including standardized indicators for “soil multifunctionality,” long-term trials across climate gradients, and co-production approaches that embed farmers’ knowledge in scalable climate-smart strategies. Intercropping designs vary widely (strip, row, relay, mixed stands), and reporting of spatial configuration, planting density, residue fate, and management history is sometimes incomplete, reducing comparability and synthesis strength.